Liquid crystal display devices have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), and video cameras, because of its portability, low power consumption, and low radiation. A typical LCD device includes an LCD panel, a backlight for illuminating the LCD panel, a backlight control circuit for controlling the backlight, and a power circuit for providing operation voltages to the LCD panel and the backlight control circuit.
Referring to FIG. 4, a typical power circuit for providing power voltages to an LCD device is shown. The power circuit 100 includes an input terminal 101, a first PWM circuit 110, a first switching mode voltage stabilizer circuit 120, a second PWM circuit 130 and a second switching mode voltage stabilizer circuit 140. When the LCD device works, an inputting voltage is respectively applied to the first PWM circuit 110 and the second PWM circuit 130 via the input terminal 101, and therefore a first pulse wave and a second pulse wave are obtained and respectively transmitted to the first switching mode voltage stabilizer circuit 120 and the second switching mode voltage stabilizer circuit 140. The first switching mode voltage stabilizer circuit 120 generates and outputs a first direct voltage according to the first pulse wave. The second switching mode voltage stabilizer circuit 140 generates and outputs a second direct voltage according to the second pulse wave. The first direct voltage is configured to drive a light source of the LCD device, such as light emitting diodes (LEDs). The second direct voltage is configured to drive a liquid crystal panel of the LCD device.
Under consideration of high cost of the PWM circuit, the power circuit 100 needs two PWM circuit 110,130 for respectively driving the light source and the liquid crystal panel of the LCD device. Thus, the costs of the power circuit 100 and the LCD device employing it are high.
What is needed, therefore, is a power circuit that can overcome the above-described deficiencies. What is also needed is an LCD device employing such power circuit.